1. No significant improvements like agriculture.
2. Increasing regulations
3. Big middle class that have no strong motivation to advance further or have "enough money" for good living (modulo individuals)
4. Growth in domain which GDP doesn't capture e.g. Open Source
5. No obvious investments opportunities e.g. Highway
And, yes, birthrates and longer retirement are probably relevant.
7. Low birth rates.
1. No significant improvements like agriculture.
2. Increasing regulations
3. Big middle class that have no strong motivation to advance further or have "enough money" for good living (modulo individuals)
4. Growth in domain which GDP doesn't capture e.g. Open Source
5. No obvious investments opportunities e.g. Highway